Pt/SO4 2−−ZrO2: The state of platinum and its relation with catalytic activity inn-hexane isomerization

1998 ◽  
Vol 63 (1) ◽  
pp. 33-40 ◽  
Author(s):  
S. R. Vaudagna ◽  
R. A. Comelli ◽  
N. S. Fígoli
Keyword(s):  
Catalytic Activity ◽  
The State

scholarly journals Synthesis and catalytic applications of combined zeolitic/mesoporous materials

2011 ◽  
Vol 2 ◽  
pp. 785-801 ◽  
Author(s):  
Jarian Vernimmen ◽  
Vera Meynen ◽  
Pegie Cool
Keyword(s):  
Catalytic Activity ◽  
Mesoporous Materials ◽  
State Of The Art ◽  
Nanoporous Materials ◽  
The State ◽  
Viscous Fluids ◽  
Formation Mechanisms ◽  
Enhanced Diffusion ◽  
Redox Catalysts ◽  
Catalytic Applications

In the last decade, research concerning nanoporous siliceous materials has been focused on mesoporous materials with intrinsic zeolitic features. These materials are thought to be superior, because they are able to combine (i) the enhanced diffusion and accessibility for larger molecules and viscous fluids typical of mesoporous materials with (ii) the remarkable stability, catalytic activity and selectivity of zeolites. This review gives an overview of the state of the art concerning combined zeolitic/mesoporous materials. Focus is put on the synthesis and the applications of the combined zeolitic/mesoporous materials. The different synthesis approaches and formation mechanisms leading to these materials are comprehensively discussed and compared. Moreover, Ti-containing nanoporous materials as redox catalysts are discussed to illustrate a potential implementation of combined zeolitic/mesoporous materials.

Effect of Pt and Pd additives on the state of the surface layer and catalytic activity of niobium oxides in the oxidation of hydrogen

2009 ◽  
Vol 45 (5) ◽  
pp. 331-337 ◽  
Author(s):  
V. V. Lesnyak ◽  
V. K. Yatsimirskii ◽  
T. D. Kinder ◽  
O. Yu. Boldyreva
Keyword(s):  
Surface Layer ◽  
Catalytic Activity ◽  
The State ◽  
Niobium Oxides ◽  
Oxidation Of Hydrogen

scholarly journals Preparation of Pd/SiO2 Catalysts by a Simple Dry Ball-Milling Method for Lean Methane Oxidation and Probe of the State of Active Pd Species

Catalysts ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 725
Author(s):  
Li Yang ◽  
Chao Fan ◽  
Li Luo ◽  
Yanyan Chen ◽  
Zhiwei Wu ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Low Temperature ◽  
Ball Milling ◽  
Methane Oxidation ◽  
Oxidation State ◽  
Catalytic Performance ◽  
The State ◽  
Pd Catalysts ◽  
Tight Contact ◽  
Milling Method

A series of Pd/SiO2 catalysts were prepared with different Pd precursors by a dry ball-milling method and used in the catalytic oxidation of lean methane at low temperature. The effect of Pd precursors on the catalytic performance was investigated and the state of the most active Pd species was probed. The results indicate that dry ball-milling is a simple but rather effective method to prepare the Pd/SiO2 catalysts for lean methane oxidation, and palladium acetylacetonate is an ideal precursor to obtain a highly active Pd/SiO2-Acac catalyst with well- and stably dispersed Pd species, owing to the tight contact between acetylacetonate and Si–OH on the SiO2 support. Besides the size and dispersion of Pd particles, the oxidation state of Pd species also plays a crucial role in determining the catalytic activity of Pd/SiO2 in lean methane oxidation at low temperature. A non-monotonic dependence of the catalytic activity on the Pd oxidation state is observed. The activity of various Pd species follows the order of PdOx >> Pd > PdO; the PdOx/SiO2-Acac catalysts (in particular for PdO0.82/SiO2-Acac when x = 0.82) exhibit much higher activity in lean methane oxidation at low temperature than Pd/SiO2-Acac and PdO/SiO2-Acac. The catalytic activity of PdOx/SiO2 may degrade during the methane oxidation due to the gradual transformation of PdOx to PdO in the oxygen-rich ambiance; however, such degradation is reversible and the activity of a degraded Pd/SiO2 catalyst can be recovered through a redox treatment to regain the PdOx species. This work helps to foster a better understanding of the relationship between the structure and performance of supported Pd catalysts by clarifying the state of active Pd species, which should be beneficial to the design of an active catalyst in lean methane oxidation at low temperature.

Behaviour of CoNaA zeolites in interaction with water

1980 ◽  
Vol 45 (1) ◽  
pp. 9-16 ◽  
Author(s):  
Blanka Wichterlová ◽  
Ludmila Kubelková ◽  
Pavel Jírů
Keyword(s):  
Catalytic Activity ◽  
Infrared Spectroscopy ◽  
Adsorbed Water ◽  
The State ◽  
Molecular Water ◽  
Oh Groups ◽  
Adsorption Of Water ◽  
Stretching Vibrations

The influence of dehydration and adsorption of water on the coordination of cations, the state of adsorbed water, and stretching vibrations of CoNaA and NaA zeolites was investigated by means of electronic and infrared spectroscopy. Complexes of Co2+ change their symmetry from octahedral through tetrahedral to planar trigonal. The role of ligands play both skeletal oxygens and molecular water. The formation of OH groups either on skeleton or on Co2+ ions was not found; the existence of these groups was assumed in the literature to explain the catalytic activity of CoNaA zeolites in the isomerization of butenes.

The state of platinum in high-silica zeolites and its catalytic activity in ethane and propane aromatization

1986 ◽  
Vol 27 (2) ◽  
pp. 219-231 ◽  
Author(s):  
O.V. Bragin ◽  
E.S. Shpiro ◽  
A.V. Preobrazhensky ◽  
S.A. Isaev ◽  
T.V. Vasina ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
The State ◽  
Propane Aromatization ◽  
High Silica ◽  
High Silica Zeolites

The state of metal ions in supported catalysts with respect to their catalytic activity in metathesis

1980 ◽  
Vol 8 (1-3) ◽  
pp. 135-145 ◽  
Author(s):  
B.N. Kuznetsov ◽  
A.N. Startsev ◽  
Yu.I. Yermakov
Keyword(s):  
Catalytic Activity ◽  
Metal Ions ◽  
Supported Catalysts ◽  
The State

Practical Picture Processing

1974 ◽  
Vol 32 ◽  
pp. 338-339
Author(s):  
T. A. Welton
Keyword(s):  
Radiation Damage ◽  
Coherence Length ◽  
Spatial Information ◽  
State Of The Art ◽  
Coherent Radiation ◽  
The State ◽  
Energy Spread ◽  
Electron Micrograph ◽  
Picture Processing ◽  
Molecular Skeleton

Various authors have emphasized the spatial information resident in an electron micrograph taken with adequately coherent radiation. In view of the completion of at least one such instrument, this opportunity is taken to summarize the state of the art of processing such micrographs. We use the usual symbols for the aberration coefficients, and supplement these with £ and 6 for the transverse coherence length and the fractional energy spread respectively. He also assume a weak, biologically interesting sample, with principal interest lying in the molecular skeleton remaining after obvious hydrogen loss and other radiation damage has occurred.

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